1. Field of the Invention:
The present invention relates to a system and method for a multicast architecture for wireless mesh networks.
2. Description of the Related Art:
Wireless communication networks, such as mobile wireless telephone networks, have become increasingly prevalent over the past decade. These wireless communications networks are commonly referred to as “cellular networks”, because the network infrastructure is arranged to divide the service area into a plurality of regions called “cells”. A terrestrial cellular network includes a plurality of interconnected base stations, or base nodes, that are distributed geographically at designated locations throughout the service area. Each base node includes one or more transceivers that are capable of transmitting and receiving electromagnetic signals, such as radio frequency (RF) communications signals, to and from mobile user nodes, such as wireless telephones, located within the coverage area. The communications signals include, for example, voice data that has been modulated according to a desired modulation technique and transmitted as data packets. As can be appreciated by one skilled in the art, network nodes transmit and receive data packet communications in a multiplexed format, such as time-division multiple access (TDMA) format, code-division multiple access (CDMA) format, or frequency-division multiple access (FDMA) format, which enables a single transceiver at a first node to communicate simultaneously with several other nodes in its coverage area.
In recent years, a type of mobile communications network known as an “ad-hoc” network has been developed. In this type of network, each mobile node is capable of operating as a base station or router for the other mobile nodes, thus eliminating the need for a fixed infrastructure of base stations.
More sophisticated ad-hoc networks are also being developed which, in addition to enabling mobile nodes to communicate with each other as in a conventional ad-hoc network, further enable the mobile nodes to access a fixed network and thus communicate with other mobile nodes, such as those on the public switched telephone network (PSTN), and on other networks such as the Internet. Details of these advanced types of ad-hoc networks are described in U.S. Pat. No. 7,072,650 entitled “Ad Hoc Peer-to-Peer Mobile Radio Access System Interfaced to the PSTN and Cellular Networks”, issued on Jul. 4, 2006, in U.S. Pat. No. 6,807,165 entitled “Time Division Protocol for an Ad-Hoc, Peer-to-Peer Radio Network Having Coordinating Channel Access to Shared Parallel Data Channels with Separate Reservation Channel”, issued on Oct. 19, 2004, and in U.S. Pat. No. 6,873,839 entitled “Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio Access System”, issued on Mar. 29, 2005, the entire content of each being incorporated herein by reference.
FIG. 1 is a block diagram illustrating an example of an ad-hoc packet-switched wireless communications network 100. Specifically, the network 100 includes a plurality of mobile wireless user terminals 102-1 through 102-n (referred to generally as nodes 102 or mobile nodes 102), and can, but is not required to, include a fixed network 104 having a plurality of access points 106-1, 106-2, . . . 106-n (referred to generally as nodes 106 or access points 106), for providing nodes 102 with access to the fixed network 104. The fixed network 104 can include, for example, a core local access network (LAN), and a plurality of servers and gateway routers to provide network nodes with access to other networks, such as other ad-hoc networks, the public switched telephone network (PSTN) and the Internet. The network 100 further can include a plurality of fixed routers 107-1 through 107-n (referred to generally as nodes 107 or fixed routers 107) for routing data packets between other nodes 102, 106 or 107. It is noted that for purposes of this discussion, the nodes discussed above can be collectively referred to as “nodes 102, 106 and 107”, or simply “nodes”.
As can be appreciated by one skilled in the art, the nodes 102, 106 and 107 are capable of communicating with each other directly, or via one or more other nodes 102, 106 or 107 operating as a router or routers for packets being sent between nodes, as described in U.S. Pat. Nos. 7,072,650, 6,807,165, and 6,873,839, referenced above.
As shown in FIG. 2, each node 102, 106 and 107 includes a transceiver, or modem 108, which is coupled to an antenna 110 and is capable of receiving and transmitting signals, such as packetized signals, to and from the node 102, 106 or 107, under the control of a controller 112. The packetized data signals can include, for example, voice, data or multimedia information, and packetized control signals, including node update information.
Each node 102, 106 and 107 further includes a memory 114, such as a random access memory (RAM) that is capable of storing, among other things, routing information pertaining to itself and other nodes in the network 100. As further shown in FIG. 2, certain nodes, especially mobile nodes 102, can include a host 116 which may consist of any number of devices, such as a notebook computer terminal, mobile telephone unit, mobile data unit, or any other suitable device. Each node 102, 106 and 107 also includes the appropriate hardware and software to perform Internet Protocol (IP) and Address Resolution Protocol (ARP), the purposes of which can be readily appreciated by one skilled in the art. The appropriate hardware and software to perform transmission control protocol (TCP) and user datagram protocol (UDP) may also be included.
Multicasting is a more efficient method of supporting group communication than unicasting or broadcasting, as it allows transmission and routing of packets to multiple destinations using fewer network resources. With the advent of widespread deployment of wireless networks, the fast-improving capabilities of mobile devices, and an increasingly sophisticated mobile work force worldwide, content and service providers are increasingly interested in supporting multicast communications over wireless networks. As more and more applications and network control protocols require multicast support, an efficient multicast architecture for wireless multi-hop mesh networks is needed.
Multicast architecture for wired networks has been designed in recent decades. However, no multicast architecture for wireless multi-hop mesh networks has been proposed and deployed. Due to the unique characteristics of wireless multi-hop networks, the multicast architecture for wired networks can not be directly extended to wireless multi-hop networks.
The capacity of pure multi-hop wireless ad hoc networks diminishes as the number of nodes increases in a network as described by P. Gupta and P. R. Kumar in “The Capacity of Wireless Networks”, IEEE Transactions on Information Theory, Issue 2, March 2000. In order to increase the capacity of multi-hop wireless ad hoc networks, fixed infrastructure nodes may be introduced into the network, as described by P. Gupta and P. R. Kumar in “The Capacity of Wireless Networks”, IEEE Transactions on Information Theory, Issue 2, March 2000, and by M. J. Miller, W. D. List and N. H. Vaidya in “A Hybrid Network Implementation to Extend Infrastructure Reach”, Technical Report, January 2003. Large scale multi-hop wireless mesh networks deploy infrastructure nodes such as an Internet Access Point (IAP) to expand the capacity of the mesh networks, and to provide access to the global internet. Multiple IAPs are connected to each other via wired or fixed wireless links through an edge router that is connected to the global internet. In the wireless domain, each routable wireless device can use the multicast routing protocol to join the multicast tree and support the multicast application. However, the multicast routing protocol designed for multi-hop wireless networks can not enable all these devices to join the global internet multicasting architecture.
The proposed multicast architecture enables the mesh networks to join the global multicast groups seamlessly, and extend the multicast support to any routable or non-routable devices in the wireless mesh networks.